A content delivery network (CDN) may comprise a network of caching infrastructure servers that delivers a piece of requested content (e.g., television content, a Web page, audio, video, data, etc.) to a user based on the proximate or geographic location of the user, the origin of the requested media and a content delivery server. A CDN typically copies the media content to a network of servers that are dispersed at geographically different locations, caching the media content at each location. When a user requests as part of a transaction a particular piece of media content that is part of a CDN, the CDN will redirect the request from the originating site's server to a server in the CDN that is closest to the user and deliver the cached content.
The CDN may also communicate with the originating server to deliver any content that has not been previously cached. The closer the CDN server is to the user geographically, the faster the content is typically delivered to the user. CDNs also provide protection from large surges in traffic. The process of bouncing through a CDN is typically transparent to the user.
On some CDN servers, when the disk cache reaches a certain threshold, e.g., 95%, of the total cache space, a process runs to evict, e.g., remove or delete, old content from the cache. This process consumes central processing unit (CPU) and more importantly input/output (I/O) capacity on the server. Further, this process can occur at any time. The probability is high that this process will in fact occur during times of high transaction activity; when the server can least afford the drain on its resources. Evicting older content maintained in the cache when a pre-determined percentage of the total cache capacity is reached drains these and other valuable resources. Because the cache will frequently reach the capacity threshold when there is a lot of use and/or transaction activity, such an evict as needed approach results in additional maintenance load during high-peak times, which can translate into poorer quality video delivered to customers.